public class Test {
    public static void main(String[] args) {
        StringBuilder stringBuilder = new StringBuilder();
        stringBuilder.append("abc").append("def");
        stringBuilder.append("ghi");
        System.out.println(stringBuilder);

    }
    public static void main2(String[] args) {
        long start = System.currentTimeMillis();
        String s = "";
        for (int i = 0; i < 10; i++) {
            s += i;
        }
        long end = System.currentTimeMillis();
        System.out.println(end - start);
        //System.out.println(s);
    }
    public static void main1(String[] args) {
        final int[] array = {1,2,3,4};
       // array = new int[]{5,6,7,8};
        array[0] = 99;

    }
}
